Importance: Although negative associations of COVID-19 pandemic high school closures with adolescents' health have been demonstrated repeatedly, some research has reported a beneficial association of these closures with adolescents' sleep. The present study was, to our knowledge, the first to combine both perspectives.
Objective: To investigate associations between adolescents' sleep and health-related characteristics during COVID-19 pandemic school closures in Switzerland.
Design, setting, and participants: This survey study used cross-sectional online surveys circulated among the students of 21 public high schools in Zurich, Switzerland. The control sample completed the survey under regular, prepandemic conditions (May to July 2017) and the lockdown sample during school closures (May to June 2020). Survey respondents were included in the study if they provided their sex, age, and school.
Exposures: High school closures during the first COVID-19 pandemic wave in Switzerland (March 13 to June 6, 2020).
Main outcomes and measures: Sleep-wake patterns, health-related quality of life (HRQoL, assessed by the KIDSCREEN-10 questionnaire), substance use (caffeine, alcohol, and nicotine), and depressive symptoms (lockdown sample only; assessed using the withdrawn/depressed scale from the Youth Self Report). Multilevel regression models were used to assess sample differences and associations of health-related characteristics with sleep duration and depressive symptoms.
Results: The total sample consisted of 8972 students, including 5308 (59.2%) in the control sample (3454 [65.1%] female) and 3664 (40.8%) in the lockdown sample (2429 [66.3%] female); the median age in both samples was 16 years (IQR, 15-17 years). During school closures, the sleep period on scheduled days was 75 minutes longer (semipartial R2 statistic [R2β*], 0.238; 95% CI, 0.222-0.254; P < .001) and the students had better HRQoL (R2β*, 0.007; 95% CI, 0.004-0.012; P < .001) and less consumption of caffeine (R2β*, 0.010; 95% CI, 0.006-0.015; P < .001) and alcohol (R2β*, 0.014; 95% CI, 0.008-0.022; P < .001). Longer sleep duration was associated with better HRQoL (R2β*, 0.027; 95% CI, 0.020-0.034; P < .001) and less caffeine consumption (R2β*, 0.013; 95% CI, 0.009-0.019; P < .001). In the lockdown sample, an inverse association was found between depressive symptoms and HRQoL (R2β*, 0.285; 95% CI, 0.260-.0311; P < .001) and a positive association was found with caffeine consumption (R2β*, 0.003; 95% CI, 0.000-0.008; P = .01).
Conclusions and relevance: In this survey study, 2 opposing associations between school closures and adolescents' health were identified: a negative association with psychological distress and a beneficial association with increased sleep duration. These findings should be considered when evaluating and implementing school closures. Furthermore, the findings provide support for delaying school start times for adolescents.